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Thermal and electrical conductivity of Fermi pocket models of underdoped cuprates: Several models of the electronic spectrum in the pseudogap state of underdoped cuprates have been proposed to explain ARPES and STM measurements, which reveal only truncated Fermi pockets instead of a full metallic Fermi surface. We co...
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Non-Abelian Anyons and Non-Abelian Vortices in Topological Superconductors: Anyons are particles obeying statistics of neither bosons nor fermions. Non-Abelian anyons, whose exchanges are described by a non-Abelian group acting on a set of wave functions, are attracting a great attention because of possible applicati...
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Double path interference and magnetic oscillations in Cooper pair transport through a single nanowire: We show that the critical current of the Josephson junction consisting of superconducting electrodes coupled through a nanowire with two conductive channels can reveal the multi-periodic magnetic oscillations. The m...
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Ballistic magnon transport and phonon scattering in the antiferromagnet Nd$_2$CuO$_4$: The thermal conductivity of the antiferromagnet Nd$_2$CuO$_4$ was measured down to 50 mK. Using the spin-flop transition to switch on and off the acoustic Nd magnons, we can reliably separate the magnon and phonon contributions to ...
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First Order Premelting Transition of Vortex Lattices: Vortex lattices in the high temperature superconductors undergo a first order phase transition which has thus far been regarded as melting from a solid to a liquid. We point out an alternative possibility of a two step process in which there is a first order transit...
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Predicted formation of superconducting platinum-hydride crystals under pressure in the presence of molecular hydrogen: Noble metals adopt close-packed structures at ambient pressure and rarely undergo structural transformation at high pressures. Platinum (Pt), in particular, is normally considered to be unreactive an...
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Periodicity in Al/Ti superconducting single electron transistors: We present experiments on single Cooper-pair transistors made of two different superconducting materials. We chose Ti and Al to create an energy gap profile such that the island has a higher gap than the leads, thereby acting as a barrier to quasiparticl...
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A Fully Quantum Mechanical Model of a SQUID Ring Coupled to an Electromagnetic Field: A quantum system comprising of a monochromatic electromagnetic field coupled to a SQUID ring with sinusoidal non-linearity, is studied. A magnetostatic flux $\Phi_{x}$ is also threading the SQUID ring, and is used to control the cou...
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Vortices and quasiparticles near the "superconductor-insulator" transition in thin films: We study the low temperature behavior of an amorphous superconducting film driven normal by a perpendicular magnetic field (B). For this purpose we introduce a new two-fluid formulation consisting of fermionized field induced vo...
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Study of grain boundary transparency in (Yb1-xCax)Ba2Cu3O bi-crystal thin films over a wide temperature, field and field orientation range: The residual low angle grain boundary (GB) network is still the most important current-limiting mechanism operating in bi-axially textured rare earth barium copper oxide (REBCO) ...
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Electron-phonon coupling in cuprate and iron-based superconductors revealed by Raman scattering: Electron-phonon coupling (EPC) is one of the most common and fundamental interactions in solids. It not only dominates many basic dynamic processes like resistivity, thermal conductivity etc, but also provides the pairing...
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Novel phase diagram for antiferromagnetism and superconductivity in pressure-induced heavy-fermion superconductor Ce$_2$RhIn$_8$ probed by In-NQR: We present a novel phase diagram for the antiferromagnetism and superconductivity in Ce$_2$RhIn$_8$ probed by In-NQR studies under pressure ($P$). The quasi-2D character o...
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Magnetic Excitations in Strained Infinite-layer Nickelate PrNiO2: Strongly correlated materials often respond sensitively to the external perturbations. In the recently discovered superconducting infinite-layer nickelates, the superconducting transition temperature can be dramatically enhanced via only ~1% compressive ...
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Response to comment on "Broken translational and rotational symmetry via charge stripe order in underdoped YBa2Cu3O6+y": Fine questions our interpretation of unidirectional-stripes over bidirectional-checkerboard, and illustrates his criticism by simulating a momentum space structure consistent with our data and corr...
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Charge-Stripe Order and Superconductivity in $\mathrm{Ir_{1-x}Pt_xTe_2}$: A combined resistivity and hard x-ray diffraction study of superconductivity and charge ordering in $\mathrm{Ir_{1-x}Pt_xTe_2}$, as a function of Pt substitution and externally applied hydrostatic pressure, is presented. Experiments are focused o...
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Optical conductivity of CuO_2 infinite-layer films: The infrared conductivity of CaCuO_2, SrCuO_{2-y}, and Sr_{0.85}Nd_{0.15}CuO_2 infinite-layer films is obtained from reflectivity measurements by taking into account the substrate contribution. SrCuO_{2-y} and Sr_{0.85}Nd_{0.15}CuO_2 exhibit extra-phonon modes and str...
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Annealing, acid, and alcoholic beverage effects on Fe1+yTe0.6Se0.4: We have systematically investigated and compared different methods to induce superconductivity in iron chalcogenide Fe1+yTe0.6Se0.4 including annealing in vacuum, N2, O2, I2 atmosphere, and immersing samples into acid and alcoholic beverages. Vacuum an...
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Multiple nodeless superconducting gaps in noncentrosymmetric superconductor PbTaSe2 with topological bulk nodal lines: Low-temperature thermal conductivity measurements were performed on single crystal of PbTaSe$_2$, a noncentrosymmetric superconductor with topological bulk nodal lines in the electronic band structur...
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Tunneling studies in a homogeneously disordered s-wave superconductor: NbN: We report the evolution of superconducting properties as a function of disorder in homogeneously disordered epitaxial NbN thin films grown on (100) MgO substrates, studied through a combination of electrical transport, Hall Effect and tunneli...
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Electronic Structure, Electron-Phonon Coupling, and Multiband Effects in MgB2: We review the current situation in the theory of superconducting and transport properties of MgB2. First principle calculations of of the electronic structure and electron-phonon coupling are discussed and compared with the experiment. We ...
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Odd-frequency pairing and Ising spin susceptibility in time-reversal invariant superfluids and superconductors: We here examine the relation between odd-frequency spin-triple even-parity (OTE) Cooper pairs and anomalous surface magnetic response in time-reversal invariant (TRI) spin-triplet superfluids and supercondu...
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On the Excitations of a Balian-Werthamer Superconductor: My contribution to this collection of articles in honor of David Lee and John Reppy on their 90th birthdays is a reflection on the remarkable phenomenology of the excitation spectra of superfluid $^3$He, in particular the B-phase which was identified by NMR and a...
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Fully dense MgB_2 superconductor textured by hot deformation: Bulk textured MgB_2 material of nearly full density showing a weak c-axis alignment of the hexagonal MgB_2 grains parallel to the pressure direction was obtained by hot deformation of a stoichiometric MgB_2 pellet prepared by a gas-solid reaction. The textur...
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Critical Current Peaks at $3B_Φ$ in Superconductors with Columnar Defects: Recrystalizing the Interstitial Glass: The role of commensurability and the interplay of correlated disorder and interactions on vortex dynamics in the presence of columnar pins is studied via molecular dynamics simulations. Simulations of dyn...
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The Garber Current Pattern: An Additional Contribution to AC Losses in Helical HTS Cables?: Conductors made of high-temperature (HTS) wires helically wound in one or more layers on round tubes (CORT) are compact, flexible, and can carry a large amount of current. Although these conductors were initially developed for...
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The Thermodynamics and the Inverse Isotope Effect of superconducting PdH and PdD under pressure: We present in this paper the thermodynamics of superconducting PdH and PdD under pressure. We make use of a general method to calculate the thermodynamics under pressure within the Migdal-Eliashberg theory. We have consid...
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Encapsulating high-temperature superconducting twisted van der Waals heterostructures blocks detrimental effects of disorder: High-temperature cuprate superconductors-based van der Waals (vdW) heterostructures hold high technological promise. One of the obstacles hindering progress is the detrimental effect of disord...
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Ab-initio Studies of (Li$_{0.8}$Fe$_{0.2}$)OHFeSe Superconductors: Revealing the Dual Roles of Fe$_{0.2}$ in Structural Stability and Charge Transfer: The recently discovered (Li$_{0.8}$Fe$_{0.2}$)OHFeSe superconductor provides a new platform for exploiting the microscopic mechanisms of high-$T_c$ superconductivity...
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$η$ collective mode as A$_{1g}$ Raman resonance in cuprate superconductors: We discuss the possible existence a spin singlet excitation with charge $\pm2$ ($\eta$-mode) originating the $A_{1g}$ Raman resonance in cuprate superconductors. This $\eta$-mode relates the $d$-wave superconducting singlet pairing channel to...
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Anomalous metallic state above the upper critical field of the conventional three-dimensional superconductor AgSnSe2 with strong intrinsic disorder: We report superconducting properties of AgSnSe2 which is a conventional type-II superconductor in the very dirty limit due to intrinsically strong electron scatterings...
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Induced ferromagnetic moment at the interface between epitaxial SrRuO$_3$ film and Sr$_2$RuO$_4$ single crystal: SrRuO$_3$ (SRO113) is an important material for device physics particularly as one of the best metallic oxide electrodes for ferroelectric devices. This oxide has moderate electron correlations with novel ...
cond-mat_supr-con
Superconducting Quantum Interference at the Atomic Scale: A single spin in a Josephson junction can reverse the flow of the supercurrent. At mesoscopic length scales, such $\pi$-junctions are employed in various instances from finding the pairing symmetry to quantum computing. In Yu-Shiba-Rusinov (YSR) states, the atom...
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Comment on "Quantum Melting of the Quasi-Two-Dimensional Vortex Lattice in $κ-(ET)_2Cu(NCS)_2$": In a recent Letter Mola et al. \cite{mola} reported magnetization measurements $M(H,\theta)$ performed on the organic superconductor $\kappa-$(ET)$_2$Cu(NCS)$_2 (T_c = 9.1$ K) as a function of the magnetic field $H$ appli...
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Exactly solvable pairing models in two dimensions: The BCS theory models electron correlations with pure zero-momentum pairs. Here we consider a family of pairing Hamiltonians, where the electron correlations are modelled with pure arbitrary-momentum pairs. We find all models in the family are exactly solvable, and pre...
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Single Crystal Growth of Cuprate Superconductor (Lu$_{0.8}$Nd$_{0.2}$)Ba$_2$Cu$_4$O$_8$ by KOH Flux Method: Single crystals of Nd-substituted LuBa$_2$Cu$_4$O$_8$ were successfully grown by the KOH flux method. The single phase of Lu$_{1-x}$Nd$_x$Ba$_2$Cu$_4$O$_8$ [(Lu,Nd)124] formed at $x = 0.2$. The compound crystal...
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Observation of novel gapped phases in potassium doped single layer p-terphenyl on Au (111): Recently, superconductivity in potassium (K) doped p-terphenyl (C18H14) has been suggested by the possible observation of the Meissner effect and subsequent photoemission spectroscopy measurements, but the detailed lattice str...
cond-mat_supr-con
The Effects of d_{x^2-y^2}-d_{xy} Mixing on Vortex Structures and Magnetization: The structure of an isolated single vortex and the vortex lattice, and the magnetization in a $d$-wave superconductor are investigated within a phenomenological Ginzburg-Landau (GL) model including the mixture of the $d_{x^2-y^2}$-wave a...
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Interplay between kinetic inductance, non-linearity and quasiparticle dynamics in granular aluminum MKIDs: Microwave kinetic inductance detectors (MKIDs) are thin film, cryogenic, superconducting resonators. Incident Cooper pair-breaking radiation increases their kinetic inductance, thereby measurably lowering their ...
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Multimodal synchrotron X-ray diffraction across the superconducting transition of Sr$_{0.1}$Bi$_2$Se$_3$: In the doped topological insulator Sr$_x$Bi$_2$Se$_3$, a pronounced in-plane two-fold symmetry is observed in electronic properties below the superconducting transition temperature $T_c \sim$ 3 K, despite the thr...
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Superconductivity-insensitive order at $q$~1/4 in electron doped cuprates: One of the central questions in the cuprate research is the nature of the "normal state" which develops into high temperature superconductivity (HTSC). In the normal state of hole-doped cuprates, the existence of charge density wave (CDW) is e...
cond-mat_supr-con
The c axis optical conductivity of layered systems in the superconducting state: In this paper, we discuss the c axis optical conductivity Re [sigma_c(omega)] in the high T_c superconductors, in the superconducting state. The basic premise of this work is that electrons travelling along the c axis between adjacent Cu...
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Group-9 Transition Metal Suboxides Adopting the Filled-Ti$_2$Ni Structure: A Class of Superconductors Exhibiting Exceptionally High Upper Critical Fields: The Ti$_2$Ni and the related $\eta$-carbide structure are known to exhibit various intriguing physical properties. The Ti$_2$Ni structure with the cubic space gr...
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Materials Informatics Reveals Unexplored Structure Space in Cuprate Superconductors: High-temperature superconducting cuprates have the potential to be transformative in a wide range of energy applications. In this work we analyse the corpus of historical data about cuprates using materials informatics and re-examine...
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High-Temperature Superconductivity Mechanism for Cuprates: Egorov and March plotted the product of resistivity and the copper spin-lattice relaxation time vs. temperature for yttrium barium copper oxide finding a minimum at temperature T greater than the superconducting temperature, heralding an electronic phase change...
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STM/STS study on large pseudogap and nodal superconducting gap in Bi2201(La) and Bi2212: In the present work, scanning tunneling microscopy/spectroscopy (STM/STS) measurements were carried out on underdoped $\rm Bi_2Sr_{2-{\it x}}La_{\it x}CuO_{6+\delta}$ and $\rm Bi_2Sr_2CaCu_2O_{8+\delta}$ to clarify the origin of ...
cond-mat_supr-con
Ginzburg-Landau expansion and the upper critical field in disordered attractive Hubbard model: We present a short review of our studies of disorder influence upon Ginzburg - Landau expansion coefficients in Anderson - Hubbard model with attraction in the framework of the generalized DMFT+$\Sigma$ approximation. A wid...
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Pairing mechanism in Fe pnictide superconductors: By applying an exact unitary transformation to a two-band hamiltonian which also includes the effects due to large pnictogen polarizabilities, we show that an attractive spin-mediated Hubbard term appears in the $d_{xz}$, $d_{yz}$ nearest-neighbour channel. This pairing...
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Comment on the paper by D. Efremov and Yu.N. Ovchinnikov "Singular ground state of multiband inhomogeneous superconductors", Phys. Rev. B 99, 224508 (2019): We show that the conclusion reported in Ref. 1, that there are no spontaneous magnetic fields in multiband superconductors that break time reversal symmetry, i...
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Signatures of a pair density wave at high magnetic fields in cuprates with charge and spin orders: In underdoped cuprates, the interplay of the pseudogap, superconductivity, and charge and spin ordering can give rise to exotic quantum states, including the pair density wave (PDW), in which the superconducting (SC) or...
cond-mat_supr-con
Measuring the Localization Length through the superconductor-insulator transition in ultrathin amorphous beryllium films: Electron transport and tunneling across the superconductor-insulator (SI) transition have been measured simultaneously for quench-condensed ultrathin amorphous beryllium films. The anomalous negat...
cond-mat_supr-con
Magnetic resonance peak and nonmagnetic impurities: Nonmagnetic Zn impurities are known to strongly suppress superconductivity. We review their effects on the spin excitation spectrum in $\rm YBa_2Cu_3O_{7}$, as investigated by inelastic neutron scattering measurements.
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Pressure effects on the electronic structure and superconductivity of (TaNb)$_{0.67}$(HfZrTi)$_{0.33}$ high entropy alloy: Effects of pressure on the electronic structure, electron-phonon interaction, and superconductivity of the high entropy alloy (TaNb)$_{0.67}$(HfZrTi)$_{0.33}$ are studied in the pressure range 0 ...
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Positive current cross-correlations in a highly transparent normal-superconducting beam splitter due to synchronized Andreev and inverse Andreev reflections: Predictions are established for linear differential current-current cross-correlations dSab/dV in a symmetrically biased three-terminal normal metal-supercond...
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Bosonic spectral density of epitaxial thin-film La1.83Sr0.17CuO4 superconductors from infrared conductivity measurements: We use optical spectroscopy to investigate the excitations responsible for the structure in the optical self-energy of thin epitaxial films of La1.83Sr0.17CuO4. Using Eliashberg formalism to inver...
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Theory of heterotic SIS Josephson junctions between single- and multi-gap superconductors: Using the functional integral method, we construct a theory of heterotic SIS Josephson junctions between single- and two-gap superconductors. The theory predicts the presence of in-phase and out-of-phase collective oscillation ...
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Bimagnon studies in cuprates with Resonant Inelastic X-ray Scattering at the O K edge. I - An assessment on La2CuO4 and a comparison with the excitation at Cu L3 and Cu K edges: We assess the capabilities of magnetic Resonant Inelastic X-ray Scattering (RIXS) at the O $K$ edge in undoped cuprates by taking La_{2}Cu...
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Single vortex fluctuations in a superconducting chip as generating dephasing and spin flips in cold atom traps: We study trapping of a cold atom by a single vortex line in an extreme type II superconducting chip, allowing for pinning and friction. We evaluate the atom's spin flip rate and its dephasing due to the vor...
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Hidden Reentrant and Larkin-Ovchinnikov-Fulde-Ferrell Superconducting Phases in a Magnetic Field in (TMTSF)$_2$ClO$_4$: We solve a long-standing problem about a theoretical description of the upper critical magnetic field, parallel to conducting layers and perpendicular to conducting chains, in (TMTSF)$_2$ClO$_4$ sup...
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Phase stiffness in an antiferromagnetic superconductor: We analyze the suppression of the phase stiffness in a superconductor by antiferromagnetic order. The analysis is based on a general expression for the phase stiffness in a mean-field state with coexisting spin-singlet superconductivity and spiral magnetism. Neel ...
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Inhomogeneity of charge density wave order and quenched disorder in a high Tc superconductor: It has recently been established that the high temperature (high-Tc) superconducting state coexists with short-range charge-density-wave order and quenched disorder arising from dopants and strain. This complex, multiscale p...
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Evidence for a universal length scale of dynamic charge inhomogeneity in cuprate superconductors: Time-resolved optical experiments can give unique information on the characteristic length scales of dynamic charge inhomogeneity on femtosecond timescales. From data on the effective quasiparticle relaxation time &#6155...
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Josephson squelch filter for quantum nanocircuits: We fabricated and tested a squelch circuit consisting of a copper powder filter with an embedded Josephson junction connected to ground. For small signals (squelch-ON), the small junction inductance attenuates strongly from DC to at least 1 GHz, while for higher freque...
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Quantum phase slip junctions: In this paper we demonstrate that, if it exists, coherent quantum phase slip is the exact dual to Josephson tunneling. We use the duality to predict kinetic capacitance and a sharp resonance in narrow wires. Biased resistively and driven at high frequency, quantum phase slip junctions shou...
cond-mat_supr-con
Type I superconductivity in the Dirac semimetal PdTe2: The superconductor PdTe$_2$ was recently classified as a Type II Dirac semimetal, and advocated to be an improved platform for topological superconductivity. Here we report magnetic and transport measurements conducted to determine the nature of the superconducting...
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Collective excitations in two-band superconductors: We investigate the eigen oscillations of internal degrees of freedom (Higgs mode and Goldstone mode) of two-band superconductors using the extended time-dependent Ginzburg-Landau theory, formulated in a work Grigorishin (2021) \cite{grig2}, for the case of two coupled...
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Dynamics of spin transport in voltage-biased Josephson junctions: We investigate spin transport in voltage-biased spin-active Josephson junctions. The interplay of spin filtering, spin mixing, and multiple Andreev reflection leads to nonlinear voltage dependence of the dc and ac spin current. We compute the voltage cha...
cond-mat_supr-con
On superconducting mechanism in the iron-based layered superconductors: It is demonstrated that SC mechanism of doped Fe-based compounds is characteristic for itinerant electron systems with coexistence of both (e-e)- and (e-h)-pairing arising due to electron-phonon and Coulomb interactions, respectively. The higher Tc...
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High-energy magnetic excitations in overdoped La$_{2-x}$Sr$_{x}$CuO$_{4}$ studied by neutron and resonant inelastic X-ray scattering: We have performed neutron inelastic scattering and resonant inelastic X-ray scattering (RIXS) at the Cu-$L_3$ edge to study high-energy magnetic excitations at energy transfers of mo...
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Pairing symmetry in BiS$_{2}-$based superconductors: The possible pairing symmetries for BiS$_{2}-$based superconductors is investigated by using a minimal two-orbital model with onsite and nearest-neighbor intraorbital attractions $V_{0}$ and $V_{1}$, respectively. By using the mean-field approximation and solving the...
cond-mat_supr-con
Gap and pseudogap evolution within the charge-ordering scenario for superconducting cuprates: We describe the spectral properties of underdoped cuprates as resulting from a momentum-dependent pseudogap in the normal state spectrum. Such a model accounts, within a BCS approach, for the doping dependence of the critica...
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Topological Anomalous Skin Effect in Weyl Superconductors: We show that a Weyl superconductor can absorb light via a novel surface-to-bulk mechanism, which we dub the topological anomalous skin effect. This occurs even in the absence of disorder for a single-band superconductor, and is facilitated by the topological sp...
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Is spontaneous vortex generation in superconducting 4Hb-TaS$_2$ from vison-vortex nucleation with $\mathbb{Z}_2$ topological order?: We propose the superconducting van der Waals material 4Hb-TaS$_2$ to realize the $\mathbb{Z}_2$ topological order and interpret the recent discovery of the spontaneous vortex generation...
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Frustrated Magnetic Interactions, Giant Magneto-Elastic Coupling, and Magnetic Phonons in Iron-Pnictides: We present a detailed first principles study of Fe-pnictides with particular emphasis on competing magnetic interactions, structural phase transition, giant magneto-elastic coupling and its effect on phonons. The...
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Design and implementation of a micro-coil induction magnetometer: We present a micron-sized induction magnetometer designed to measure the magnetic response of superconducting mesoscopic samples. The device is manufactured using the Memscap PolyMUMPs process and consists of two octagonal planar parallel micro-coils cov...
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SU(4) Dynamical Symmetry and the Origin of Pseudogaps: This paper has been withdrawn by the author due to incomplete interpretation for the results.
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A Terraced Scanning Superconducting Quantum Interference Device Susceptometer with Sub-Micron Pickup Loops: Superconducting Quantum Interference Devices (SQUIDs) can have excellent spin sensitivity depending on their magnetic flux noise, pick-up loop diameter, and distance from the sample. We report a family of scann...
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Spin-excitation anisotropy in the nematic state of detwinned FeSe: The origin of the electronic nematicity in FeSe is one of the most important unresolved puzzles in the study of iron-based superconductors. In both spin- and orbital-nematic models, the intrinsic magnetic excitations at $\mathbf{Q}_1=(1, 0)$ and $\mathb...
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Exploring the vortex phase diagram of Bogoliubov-de Gennes disordered superconductors: We study the interplay of vortices and disorder in a two-dimensional disordered superconductor at zero temperature described by the Bogoliubov-de Gennes (BdG) self-consistent formalism for lattices of sizes up to $100\times100$ whe...
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Physical mechanisms of timing jitter in photon detection by current carrying superconducting nanowires: We studied timing jitter in the appearance of photon counts in meandering nanowires with different fractional amount of bends. Timing jitter, which is the probability density of the random time delay between photon...
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1D Bose Gases in an Optical Lattice: We report on the study of the momentum distribution of a one-dimensional Bose gas in an optical lattice. From the momentum distribution we extract the condensed fraction of the gas and thereby measure the depletion of the condensate and compare it with a theorical estimate. We have ...
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Band-mixing-mediated Andreev reflection of semiconductor holes: We have investigated Andreev-reflection processes occurring at a clean interface between a $p$-type semiconductor and a conventional superconductor. Our calculations are performed within a generalized Bogoliubov-de Gennes formalism where the details of the...
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Extraordinary magnetoresistance in graphite: experimental evidence for the time-reversal symmetry breaking: The ordinary magnetoresistance (MR) of doped semiconductors is positive and quadratic in a low magnetic field, B, as it should be in the framework of the Boltzmann kinetic theory or in the conventional hopping ...
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Thermal evolution of antiferromagnetic correlations and tetrahedral bond angles in superconducting FeTe$_{1-x}$Se$_x$: It has recently been demonstrated that dynamical magnetic correlations measured by neutron scattering in iron chalcogenides can be described with models of short-range correlations characterized by p...
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Electronic structure and Fermi surface of iron-based superconductors R2Fe3Si5 (R = Lu;Y;Sc) from first principles: Electronic structures of three superconducting rare-earth iron silicides (Lu;Y;Sc)2Fe3Si5 and non-superconducting Lu2Ru3Si5, adopting a tetragonal crystal structure (P4/mnc), have been calculated employi...
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Field dependence of the vortex core size in a multi-band superconductor: The magnetic field dependence of the vortex core size in the multi-band superconductor NbSe2 has been determined from muon spin rotation measurements. The spatially extended nature of the quasiparticle core states associated with the smaller gap l...
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Electron Correlations in the High Tc-Compounds: Ab-initio correlation results for an idealized high Tc-compound are compared to density functional (DF) calculations for the same system. It is shown that and why the DF-charge distribution is wrong. The largest deficiency arises for the Cu-d(x2-y2)-occupation, originatin...
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Structural and Magnetic Instabilities of La$_{2-x}$Sr$_x$CaCu$_2$O$_6$: A neutron scattering study of nonsuperconducting La$_{2-x}$Sr$_x$CaCu$_2$O$_6$ (x=0 and 0.2), a bilayer copper oxide without CuO chains, has revealed an unexpected tetragonal-to-orthorhombic transition with a doping dependent transition temperature...
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Staggered Pairing Phenomenology for UPd_2Al_3 and UNi_2Al_3: We apply the staggered-pairing Ginzburg-Landau phenomenology to describe superconductivity in UPd_2Al_3 and UNi_2Al_3. The phenomenology was applied successfully to UPt_3 so it explains why these materials have qualitatively different superconducting phase di...
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Superconductivity in silicon: a review: Silicon, one of the most abundant elements found on Earth, has been an excellent choice of the semiconductor industry for ages. Despite it's remarkable applications in modern semiconductor-based electronic devices, the potential of cubic silicon in superconducting electronics rem...
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Field Dependence of the Superconducting Basal Plane Anisotropy of TmNi2B2C: The superconductor TmNi2B2C possesses a significant four-fold basal plane anisotropy, leading to a square Vortex Lattice (VL) at intermediate fields. However, unlike other members of the borocarbide superconductors, the anisotropy in TmNi2B2C...
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High-pressure synthesis and superconductivity of the novel Laves phase BaIr2: Superconductors comprising 5d transition metals of Ir and Pt have been widely explored because they have the potential of unique superconductivity caused by the strong spin-orbit interaction (SOI). We successfully synthesized BaIr2, the las...
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Minimal timing jitter in superconducting nanowire single photon detectors: Using two-temperature model coupled with modified time-dependent Ginzburg-Landau equation we calculate the delay time $\tau_d$ in appearance of growing normal domain in the current-biased superconducting strip after absorption of the single ph...
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Switching current distributions and subgap structures of underdoped (Hg,Re)Ba2Ca2Cu3O8+d intrinsic Josephson junctions: We have investigated the intrinsic Josephson properties in slightly underdoped (Hg,Re)Ba2Ca2Cu3Oy [Hg(Re)1223] intrinsic Josephson junctions (IJJs) with a dimension of 1.0x1.5x0.11 um^3. The current...
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Superuid density in overdoped cuprates: thin films versus bulk samples: Recent study of overdoped La$_{2-x}$Sr$_x$CuO$_4$ cuprate superconductor thin films by Bo\v{z}ovi\'{c} {\it et al.} has revealed several unexpected findings, most notably the violation of the BCS description which was believed to adequately describ...
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Electronic structure in one-Fe Brillouin zone of iron-pnictide superconductor CsFe$_2$As$_2$: The multiband nature of iron-pnictide superconductors is one of the keys to the understanding of their intriguing behavior. The electronic and magnetic properties heavily rely on the multiband interactions between different ...
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High-temperature superconductivity in one-unit-cell FeSe films: Since the dramatic interface enhancement of superconducting transition temperature (Tc) was reported in one unit-cell FeSe film grown on SrTiO3 substrate (1-UC FeSe/STO) by molecular beam epitaxy (MBE), related research on this system has become a new fron...
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Scanning Tunneling Spectroscopy and Vortex Imaging in the Iron-Pnictide Superconductor BaFe$_{1.8}$Co$_{0.2}$As$_2$: We present an atomic resolution scanning tunneling spectroscopy study of superconducting BaFe$_{1.8}$Co$_{0.2}$As$_2$ single crystals in magnetic fields up to $9 \text{Tesla}$. At zero field, a single ...
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Electromagnetic response of superconductors and optical sum rule: The interrelation between the condensation energy and the optical sum rules has been investigated. It has been shown that the so called 'partial' sum rule violation is related mainly to a temperature dependence of the relaxation rate rather than to the a...
cond-mat_supr-con
Gapless helical superconductivity on the surface of a three-dimensional topological insulator: Recent angle-resolved photoemission experiments have observed a proximity-induced superconducting gap in the helical surface states of a thin film of the 3D topological insulator Bi$_2$Se$_3$ grown on a superconducting NbSe...
cond-mat_supr-con
Microscopic mechanism for fluctuating pair density wave: In weakly coupled BCS superconductors, only electrons within a tiny energy window around the Fermi energy, $E_F$, form Cooper pairs. This may not be the case in strong coupling superconductors such as cuprates, FeSe, SrTiO$_3$ or cold atom condensates where the p...
cond-mat_supr-con